With the development of compound or split limb bows and the widespread use thereof, there has arisen the attendant problem of replacing defective or worn bow strings, tension cables, wheels, etc., and providing and maintaining the proper tension on the bow string.
As is well known to those skilled in the art, the most popular form of compound bow includes two or more eccentrically mounted pulleys or wheels pivotally attached relative the bow limbs and serving to support and control the movement of a bow string which in turn is connected to a tension cable. The popularity of the compound bow is mainly due to the advantage provided in the reduced pull force required at full draw together with the resulting increase in accuracy. The pull on the bow string is high at the beginning of the draw but the arm at this point is able to exert maximum force. As the draw progresses a little beyond mid-point, there is an overcenter action on the eccentrically mounted pulleys or wheels which decreases the draw force needed to maintain the bow string in the drawn position without decreasing the energy stored in the limbs of the bow. Thus, at full draw it is relatively easy to hold the arrow and bow string and much easier to perfect aiming technique and proper finger release resulting in increased accuracy.
As will be appreciated by those familiar with compound bows, the stringing or outfitting of such a bow with its tension cable and bow string is very critical in order to achieve a proper balance or synchronization of the eccentrically mounted pulleys or wheels. The stringing or rigging makes it virtually impossible to unstring the bow when it is not in use. Thus, the limbs of compound bows are always under significant stress, which eventually leads to a degradation of the limb materials, a stretching of the bow string and a reduction in the bow weight (the amount of force needed to flex the bow limbs to a condition of full draw of the bow string) with time for a given setting of the bow. This means that a periodic retuning of compound bows is needed to maintain desired performance levels. Also, over a period of time and with use, various elements of a compound bow, such as the bow string, the tension cable, a wheel or wheels, etc., need to be replaced and/or repaired.
In the prior art there are some devices which allow the bow string to be changed on a compound-type bow. For example, U.S. Pat. No. 3,055,655 discloses a bow press including a base with tiltable arms extending transversely therefrom. Each arm has on its remote end a roller which accommodates the tip ends of the limbs of the bow to be strung. The bow is supported on the rollers and a stirrup is buckled to the handle with the concave portion of the bow facing upward. A foot placed in the stirrup is used to depress the handle, flex the arms, and restringing of the bow may be accomplished while the foot remains in position.
U.S. Pat. No. 3,000,628 is even more primitive in that it secures a frame to a wall and two spaced spools are mounted extending transversely from the vertical framework. The handle of a bow fits in one spindle and one limb in the other. The bow is restrung by a manual operation with the operator pulling on the opposite limb of the bow to release tension on the string.
U.S. Pat. No. 4,074,409 discloses a bow stringing apparatus with attachment brackets for attaching a pull cord to the bow cables between the opposite eccentric pulley wheels and the bow string attachment points. It is a manual operation which allow no release prior to completion of restringing. The pull cord utilizes a low friction sheath member and a sliding locking bar for pulling tension on the bow and locking the bow in a compressed position while changing the bow string.
U.S. Pat. No. 4,599,987 discloses a bow press for restringing a split limb bow and includes a pair of spaced apart bars which engage the exterior of the limbs via slots formed therein. The bars are connected by cords. A rotatable lever is connected to the cords intermediate the bars. When manually rotated from a first position to a second position, the handle causes inward compression of the limbs toward each other. An adjustment rod, which is variable in length, reduces or extends the length between the two bars to accommodate bows of various sizes.
U.S. Pat. No. 5,022,377 provides for a frame having transversely extending pegs at its remote ends. A bow is mounted in the framework with the concave side facing upward and the limbs of the bow engaging the aforementioned pegs. A yolk fits over the handle and it is mounted on a threaded rod which passes through a mating threaded block secured to the framework. Rotation of the rod moves the yoke which pushes the handle away from the block and thereby flexes the limbs of the bow upward as the handle is depressed.
Three bow presses are displayed in the Spring Edition of 1992 of the Discount Warehouse, Inc. catalog for Bow Hunters and each involves a pulleytype arrangement where two cable connections are attached to a framework with their ends secured around a bow at the junction between the handle and the limbs. The framework in each case includes a roller at the remote ends of the framework and a pulley is used by hand operation to pull the handle down to deflect the limbs.
The problem with the prior art as identified above is the potential for separation which occurs as a result of rolling or sliding contact between transversely extending pegs on the framework and the laminated compound bow surface during the compression operation. The apparatus occasionally causes separation of the laminations and more frequently abrades the surface of the bow.